Effects of ultrasonic irradiation on the viscosity of fuel oils

Letters to the Editor

Effects

of ultrasonic

irradiation

on the viscosity

of fuel oils

Makoto Nagai, Hideto Seiyama and Motomu Kasagi The National Defense Academy, Hashirimizu, Yokosuka, Kanagawa-ken, (Received 11 April 1981)

Japan

Fuel oil A, 5 and C, and a residual oil from vacuum distillation (R-Oil) have been irradiated with 25kHz ultrasonic waves (150W) at 50°C for 10 h. The observed increases in the kinematic viscosity (AI%) are: fuel oil A, 0.3%; fuel oil B, 5.3%; fuel oil C, 17.6%; and R-Oil 5.5%. The value and sign of Av are found to change with the sample weight in the flask. I .r. measurements show that ultrasonic irradiation causes the intensities of CH2 and CH, to decrease slightly. The ultrasonic energy appears to be used in the breakingup and/or coupling of the petroleum molecules. (Keywords:

fuel oil; ultrasonic

irradiation;

polymerization;

The amounts of coal which can be extracted with some solvents has been shown to be increased significantly by the use of the ultrasonic irradiation.’ -3 Ultrasonic irradiation has been used also for the degradation of petroleum molecules, and several industrial applications have been proposed.4v5 However, its mechanism has not been investigated in any detail. In this Letter the changes in the viscosity of petroleum samples caused by the ultrasonic irradiation are described. The petroleum samples used are fuel oil A, Band C, and a residual oil from vacuum distillation (R-Oil). The elemental analyses and kinematic viscosities (m2 s-l) measured by the usual procedure6 at 50°C are given in Table 1.

Average viscosities are given for fuel oil C and R-Oil because they vary slightly with the time of measurement. No distinct changes were observed between the results of elemental analyses before and after the ultrasonic irradiation of the samples. The ultrasonic irradiation apparatus (Cho-ompa Kogyo Co. Ltd.: USV-1 SOV-4A)generates waves with 25 kHz frequency (150 W). The ultrasonic energy was directed to a 100 ml glass flask containing the sample (17 g except for fuel oil C and R-Oil, 20 g) maintained at a given temperature in air. After 10 h irradiation at 50°C the observed kinematic viscosity and its increased fraction (AI@,)were: fuel oil A, 1.589 x 10P6m2 s-l (0.3%);fueloilB,2.896 x lo-’ m2s-’

viscosity)

(5.3%); fuel oil C, 2.157x 10m4 m2 s-’ (17.6%); R-Oil, 4.303 x lop3 m2 s-l (5.5%). Careful i.r. measurements of irradiated and nonirradiated samples showed slight decreases in the intensities of CH, and CH, (1460, 1375 and 720 cm-‘), indicating the polymerization of the petroleum molecules by the ultrasonic energy. A slight oxidation’ of fuel oils is thought to occur, because the intensity of CO (1030 cm- ‘) signal increases slightly. The precise kinematic viscosity of fuel oil B was measured before and after irradiation for a given period of time (Figure 1). The viscosities before irradiation were almost the same, but those after irradiation had increased significantly. The data after 120 min were found to fit a simple firstorder equation. Applying the usual absolute reaction theory,2 AH* and AS* values (the apparent activation enthalpy and entropy of the polymerization reaction induced by the ultrasonic energy, respectively) are

Tab/e 7 Analyses of fuel oils and residual oil Ultimate Sample Fuel oil Fuel oil Fuel oil Residual

A B C oil

analysis (wt %)

C

H

N

S

Kinematic viscosity (mZ s-l)

87.1 86.7 86.4 86.2

13.0 12.0 11.5 10.7

<0.3 <0.3 <0.3 <0.3

0.4 1.9 2.3 3.1

1.585 x 10” 2.750 x 10-s 1.835x 10-4 4.078 x 10-3

0016 2361/82/l I1 16&02$3.00 @ 1982 Butterworth & Co (Publishers)

1160

FUEL, 1982,

Ltd.

Vol 61, November

Figure 1 Kinematic viscosity versus ultrasonic irradiation time for fuel oil 8. -0, Before irradiation. - -,After irradiation; irradiated at: A, 4O’C; 0, 5o°C; A, 60°C; l,7OoC; measured at 50°C

Letters to the Editor

This phenomenon may be explained as follows: The ultrasonic energy is utilized initially to break up the petroleum molecules and the resultant free radicals’ do not recombine easily when the sample weight in the flask is large. However, when the sample weight is small, the concentration of free radicals produced becomes relatively higher and the coupling of the radicals is easier. Accordingly, the polymerization of petroleum molecules may apparently take place. This explanation does not exclude the possibility that such reactive petroleum molecules as olefins should react with the free radicals produced. These results with fuel oils appear to agree with those reported by Alexander and Fox’ and Henglein” who found that ultrasonic irradiation caused degradation and/or polymerization of synthetic polymers.

l

-8

t

^^

U

.-

cu

4u Sample

__

60

weight(g)

1

Increase in kinematic viscosity (Av) versus sample weight in flask. - 0, Fuel oil C (y = -0.31x + 16.4). -0, residual oil (y = -0.37% + 12.3); irradiated at 50°C for 10 h.,

Figure2

measured

REFERENCES

at 50°C

2 3 4 5

obtained for this reaction; i.e. 7.1 kJ mol-’ and -240 J K - ‘, respectively. The value of Av (%) by the irradiation at 50°C is found to vary with the sample weight in the flask. Results with fuel oil C and R-Oil are shown in Figure 2. The sign of Av changes from positive to negative with increase in the sample weight. Fuel oil B has similar behaviour.

Thermal decomposition

6 7 8

9 10

Kirkby, W. A., Lakey, J. R. A. and Sarjant. R. J. Fuel 1954,33,480 Anderson, L. L., Shifai, M. Y. and Hill, G. R. Fuel 1974, 53, 32 Tsuboi, H., Nagotani, K., Nagai, M., Nakano, M. and Kasagi, M. J. Fuel Sot. Jpn. 1978, 57,918 Ueda, S. Japan Kokai 1975, 76134701 (Chem. Absr. 1976, 86, 92979~) Urazgaliev, B. U., Khasanov, Zh. D. and Goryaev, M. 1. Tr. Inst. Khim. Nefti Prir. Solei, Akad. Nauk Kaz. SSR 1970.2,9 (Chem. Abst. 1972, 16, 156344~) JIS K 2283, 1980 Oelert, H. H. and Tan, T. G. Er&l u. Kohle, 24, 743 Nagai, M., Sakuda, K., Kawamura, K., Ishikawa, Y., Nakano, M. and Kasagi, M. Sci. Eng. Reps. National De&nse Academy (Japan) 1980, 18, 309 Alexander, P. and Fox, M. J. Polym.Sci. 1954,12, 533 Henglein, A. Makromol. Chem. 1955, 15, 188

of 1,4-diphenylbutane

Ming-Hong Hung and Leon M. Stock Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA (Received 22 March 1962)

To obtain information relevant to possible reaction pathways in coal liquefaction and gasification reactions, experiments were carried out to elucidate the pathways involved in the thermal decomposition of 1,4_diphenylbutane. The resultsestablished unambiguouslythat thethermal decomposition products arise via free radical pathways and not by a retroene process as has been proposed. (Keywords: decomposition reactions; chemical reactions; 1,4-diphenylbutane)

Coal liquefaction and gasification reactions may occur by several different routes. As a consequence, free radical pathways and pericyclic retroene reactions have both received attention in discussions of the thermal decomposition reactions of hydrocarbons such as 1,2diphenylethane, 1,3_diphenylpropane, and 1,4diphenylbutane.’ - ’ The available kinetic data strongly suggest that 1,2_diphenylethane and 1,3_diphenylpropane selectively undergo decomposition by radical processes over a considerable temperature range.‘-’ In brief, the decomposition of 1,Zdiphenylethane is a first-order 0016-2361/82/111161-03$3.00 @ 1982 Butterworth & Co (Publishers)

Ltd.

process with an activation energy of x260 kJ mol-‘.4,5 This observation and the product distribution suggest that the reaction proceeds by carbon-carbon bond scission to give benzyl radicals which abstract hydrogen atoms from the starting material to give other productforming radical intermediates (equations (1) and (2)):2*4,s C,H,CH,CH&H,

z~C,H,CH~.

C,H,CH*. + C,H,CH&H&H,Z C,H,CH, +C,H$H,CHC,H,

FUEL,

1982,

Vol 61, November

(1) (2)

1161